[...] beating a Lvl 13 Onix with a Lvl 3 oddish with one leech seed [...]
Did you mean to say Bellsprout? Because Oddish isn't available in Let's Go, Eevee!.
[...] Nintendo is allergic to difficulty options [...]
Junichi Masuda has for the longest time been of the mindset that the games shouldn't be too demanding (i.e. difficult) or boring for kids, which has inevitably led to the dumbing down of the games over the years. I'm sure he means well, but that's an awful mentality to have, in all honesty; it's shallow and unfair, and a very condescending outlook on kids and their intelligence.
This franchise will always play it safe, no matter what; this is Nintendo's Call of Duty, their golden goose, and they know no matter what they churn out, the blind loyals will be all over it—just look at the sales of Pokémon Brilliant Diamond and Shining Pearl, 13+ million units sold for what's essentially a glorified port. I frankly believe the series lost momentum and stagnated for so long that it became devoid of any ambition, even direction, to the point most fans just grew complacent; this slow descent into mediocrity I think began with X and Y and was aggravated sorely with Sword and Shield. The fact Pokémon Battle Revolution, a game from 2006 for the Wii, has more personality and soul than their latest entry in the series prior to Legends: Arceus speaks volumes. Mind you, Legends: Arceus isn't without its faults, it seems like a step in the right direction, as they're trying to take the franchise into new territory, but it really could've benefited from staying in development for a bit longer, which hopefully won't be the same critique Scarlet and Violet get nine months from now. I know this is probably going to be a hot take, but GameFreak is just a couple of levels away from evolving into EA...I mean, look at Square-Enix.
Personally, as a fan, I would love no more than to see a Pokémon game aimed toward its mature audience, the ones that like me have been with it since the very beginning and would like to see a more adult-oriented take on the series...BUT, we all know that is and will always remain a chimera since that's never been Nintendo's primary demographic. I will always hold this series near and dear to my heart, but for a twenty-plus-year-old franchise, it's still rough around the edges.